Some crops grow better under raised solar panels than they do in full sun

Honey producers Travis and Chiara Bolton keep bees at three solar farms where developers seeded native plants underneath and around panels. “The advantage to these sites is that they are intentionally planted for pollinators,” says Travis Bolton. “At these sites they’re really trying to get them back to a native prairie, and that’s a benefit to us.”

Native plants have replaced turfgrass and gravel as the go-to bedding for solar gardens in Minnesota. More than half of the 4,000 acres (1,600 hectares) of solar farms built in 2016 and 2017 feature native plants that not only benefit pollinators but also beautify the site.

Although Minnesota may be in the vanguard of encouraging solar farm developers to grow native plants, it is far from the only place studying how solar farms can harvest more than just energy. Universities in the United States, Germany and elsewhere are testing the concept of “dual use farming,” as some advocates call it, where crops grow below canopies of solar panels. They are finding they grow just fine—and, in some cases, better than crops in full sun.

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ALL KINDS OF BENEFITS

Adding plants to solar farms offers all kinds of benefits to the facilities’ primary aim of reducing carbon emissions and expanding renewable energy. And native and crop vegetation can help improve the health of pollinators, which are threatened by habitat loss, pesticide poisoning, poor nutrition, disease, decreased genetic diversity and a host of other factors. As a result, managed honeybee colonies used for honey production declined from 5.7 million in the 1940s to around 2.7 million today. Pollinators have an enormous impact on the economy, too, by annually contributing US$24 billion to the nation’s economy.

“Solar development is happening on a massive scale as lands are being converted from agricultural land or unused land into solar projects,” says Jordan Macknick, energy-water-land lead analyst with the National Renewable Energy Laboratory (NREL), which funds research on the impact of native and crop plants grown in solar farms. “That represents an amazing opportunity to improve our agriculture and improve our food security while developing energy at the same time.”

NREL-funded research found growing native plants could reduce land acquisition costs, reduce weed control costs and slow panel degradation.

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PILOT PROJECTS

Pilot projects in Massachusetts, Arizona, Germany, China, Croatia, Italy, Japan and France look encouraging for mixing crops with solar panels, referred to as “dual use” farms because they offer both agricultural and electrical production. “So far, the pilots have been extremely successful in showing that you can grow crops and make electricity at the same time,” Macknick says.
A dual-use farm operated by the University of Massachusetts–Amherst grows a variety of plants—peppers, beans, cilantro, tomatoes, swiss chard, kale—below solar panels elevated roughly 7.5 to 9 feet (3 meters) or more above ground to allow for easier harvesting mainly by hand. Project researchers have found that 1- to 1.2-meter (3- to 4-foot) gaps between panel clusters led to crop yields almost the same as what they would have been in full sun sites.


One of the first concepts for mixing solar and agriculture, dubbed “agrophotovoltaics” (APV), was developed more than three decades ago by physicist Adolf Goetzberger. The research institute Goetzberger created—the Fraunhofer Institute for Solar Energy Systems—finally got around to building its own dual-use farm on one-third of a hectare (just over three-quarters of an acre) at an existing farm cooperative a few years ago. The institute elevated 720 solar panels high enough for farm machinery to harvest plants underneath and nearby, according to a 2017 press release.


The researchers planted wheat, potatoes, celeriac and clover grass in the open and under the panels and compared the yields. Solar shading decreased production 5.3 percent to 19 percent. Yet electricity from the panels, which capture both indirect and direct light, was used to power a crop processing plant and electric farm machinery, offsetting those costs and increasing land use efficiency by 60 percent.

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Original text: https://www.scientificamerican.com/article/solar-farms-produce-power-and-food/